Castors for chairs and other articles of furniture

ABSTRACT

A castor for a chair comprises a wheel rotatably mounted in a housing which is pivotal about a substantially vertical axis spaced from the axis of the wheel. The housing includes an abutment surface arranged on the other side of the vertical axis to the axis of the wheel and extending below the axis of the wheel. When the chair is tilted, the abutment surface contacts the floor to prevent the chair from overturning.

United States Patent Drabert 51 Sept. 19, 1972 154] CASTORS FOR CHAIRS AND OTHER 1,731,640 10/1929 Thurlby et a1. ..16/34 ARTICLES OF FURNITURE 2,280,732 4/1942 Thum ..297/310 [72] Inventor: Fritz Dnbert, Minden/Westphalia, 2'423'659 7/1947 Germany 2,613,389 10/1952 2,812,041 11/1952 Mugler "16/18 CG [73] Assignee: hjmden/Westphalia,

G y if Primary Examiner-Bobby R. Gay 22 Filed: Nov. 17 197 Assistant Examiner-Doris L. Troutman Attorney-Mason, Mason & Albright [21] App1.No.: 90,275

[57] ABSTRACT [30] Foreign Application Priority A castor for a chair comprises a wheel rotatably June 18, 1970 Germany ..P 20 29 902.9 mounted in a housina which is pivotal about a substantially vertical axis spaced from the axis of the wheel. [52] U.S. Cl ..l6/l8, 297/310 Th using includes an abutment surface arranged [51] Int. Cl. .3601: 33/00 on th ther side of the vertical axis to the axis of the [58] Field of Search ..16/18, 35, 34; 297/310; wh l and ex ending below the axis of the wheel.

248/351 When the chaitis tilted, the abutment surface contacts the floor to prevent the chair from overturning. 56 Re! ees Cited 1 1 C1a|m,8 Drawing Figures 2,566,855 9/1951 Reinhardt..,............16/18 CG I l 2 11111 "1"" N 0 Iv} VENTOR Wyn, b l

I ATTORNEYS PATENTEDSEP 19 I 12 3.691. 590

SHEEI 3 0F 3 INVEN R FRIT z ABERT CASTORS FOR CHAIRS AND OTHER ARTICLES OF FURNITURE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to castors for articles of furniture, for example, chairs and the like.

2. Description of the Prior Art When chairs mounted on hitherto proposed castors are used without due care, occasional mishaps occur. The occupant of the chair may lean sideways beyond the edge of the chair or may lean too far back or, may sit down on the front edge of the chair, bending forward as he does so. Then, if the castor on the side concerned should chance to be turned inwards, the spread of the chair legs at that point will be reduced and the chair may overturn as the occupant leans over, particularly if the chair is a swivel chair.

The object of the invention is to overcome this disadvantage.

SUMMARY OF THE INVENTION According to the present invention, there is provided, in a castor comprising a housing, a wheel rotatably mounted in said housing, and means for mounting said housing for pivotal movement about an upwardly extending axis spaced from the axis of rotation of the wheel, the improvement comprising, abutmerit means carried by said housing and arranged to contact a surface on which said castor is supported when said upwardly-extending axis is tilted.

Further according to the present invention, there is provided, in a castor supporting an article of furniture on a surface, a housing, a wheel rotatably mounted in said housing, and means pivotally mounting said housing on said article for pivotal movement relative thereto about a substantially vertical axis spaced from the axis of rotation of the wheel, the improvement comprising abutment means mounted on said housing, said abutment means being spaced on the other side of said vertical axis to the axis of rotation of the wheel and extending below the axis of rotation of the wheel.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which:

FIG. I is a side elevation, partialIy in section of one form of castor in accordance with the present invention;

FIG. 2 is a plan of the castor shown in FIG. 1;

FIG. 3 is a side elevation, partially in section, of another form of castor in accordance with the present invention;

FIG. 4 is a plan of the castor shown in FIG. 3;

FIG. 5 is a plan of a modified form of the castor shown in FIG. 3;

FIG. 6 is a side elevation of a chair mounted on castors proposed hitherto;

FIG. 7 is a side elevation of a chair mounted on castors in accordance with the invention; and

FIG. 8 is a perspective view of a further form of castor in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In chairs mounted on castors proposed hitherto the danger of overturning is greatest when the wheels of the castors are turned inwards as shown in FIG. 6. In this condition, the distance PI-PZ between the points of contact between the wheels and the floor is less than the spread 81-82 of the chair legs by approximately twice the horizontal distance between the vertical pivotal axis of the castor and the axis of rotation of the wheel.

When the chair is moved along the ground the castors turn automatically about their pivotal axes to assume their correct position.

In the castor shown in FIGS. I and 2, the castor wheel 1 is accommodated in a housing 2 constructed to prevent the chair from overturning. The housing 2 comprises abutment means in the form of a substantially straight bearing edge 4 arranged on the other side of the vertical pivotal axis 3 of the castor to the rotational axis 6 of the wheel I and extends below the rotational axis 6 of the wheel I.

The embodiment shown in FIGS. 3 and 4 is similar to the previous embodiment except that the abutment means is in the form of a lip 5 which defines a flat bearing face located in a corresponding position to the edge The bearing edge 4 and bearing face 5 lie substantially parallel to the rotational axis of the wheel I and the bearing face 5 terminates in a straight edge lying parallel to the rotational axis of the wheel I.

In the modified form shown in FIG. 5, the bearing face 5a is widened, thereby increasing the area of the abutment means.

Preferably, the bearing edge 4 or the bearing face 5, 50 carries a facing (not shown in the drawings) on the surface thereof which lies towards the floor. This facing comprises a material which will increase the coefficient of friction between the bearing edge or face and the floor but which does not damage the floor.

With the chair in its nonnal position, the distance a between the bearing edge 4 or bearing face 5, 5a and the floor is relatively small, for example about 3 mm., depending on the nature of the floor.

It should be noted that the distance b between the pivotal axis 3 of the castor and the bearing edge 4 or bearing face 5, 5a is of importance in determining the effectiveness of the castor in preventing the chair from overturning. In the castors particularly described, this distance is between about 20 and 40 mm., although the invention is naturally not limited to this particular range. What matters is that there should be a sufficient leverage between the pivotal axis 3 and the bearing edge 4 or bearing face 5, 5a.

In the embodiment described, if the chair mounted on the castors be tilted from its normal position, the bearing edge 4 or bearing face 5, 50 comes to bear on the floor as soon as the angle of tilt amounts to about 4, so that the wheel 1 cannot rotate and the chair is prevented from moving along the floor. Contact of the bearing edge or face with the floor also serves to increase the spread of the chair legs by the distance b.

The bearing edge 4 or bearing face 5, and in particular the bearing face 50, as it meets the floor, lies parallel to the latter, ensuring a proper nonslip contact.

In the examples described hitherto, the abutment means, i.e., the bearing edge 4 and bearing faces 5, 5a form an integral part of the housing 2. The abutment means can alternatively be mounted on the housing as shown in FIG. 8. in the embodiment of FIG. 8, the abutment means in effect defines a flat bearing face corresponding to the face 5.

What is claimed is:

1. In combination a chair having a base, and

a plurality of castors supporting the base from a supporting surface, each castor'comprising a housing,

a wheel rotatably mounted in said housing for rotation about a substantially horizontal axis means mounting said housing on said base for pivotal movement relative thereto about a substantially vertical axis spaced from the said horizontal axis on one side thereof, and

abutment means rigid with said housing and spaced from the vertical axis on the other side of the horizontal axis, said abutment means having a straight end edge extending parallel to the said horizontal axis and lateral edges extending transversely to the end edge, the end edge and the lateral edges lying in an imaginary plane below the said horizontal axis, when the chair is occupied and each said castor is in contact with supporting surface, the abutment means being spaced from the supporting surface with the said plane being inclined to the supporting surface, and when the chair is tilted whereby at least one castor is raised from the supporting surface, the abutment means of other castors contacts the supporting surface with the said imaginary plane of the abutment means lying in the plane of the supporting surface.

i t i i i 

1. In combination a chair having a base, and a plurality of castors supporting the base from a supporting surface, each castor comprising a housing, a wheel rotatably mounted in said housing for rotation about a substantially horizontal axis means mounting said housing on said base for pivotal movement relative thereto about a substantially vertical axis spaced from the said horizontal axis on one side thereof, and abutment means rigid with said housing and spaced from the vertical axis on the other side of the horizontal axis, said abutment means having a straight end edge extending parallel to the said horizontal axis and lateral edges extending transversely to the end edge, the end edge and the lateral edges lying in an imaginary plane below the said horizontal axis, when the chair is occupied and each said castor is in contact with supporting surface, the abutment means being spaced from the supporting surface with the said plane being inclined to the supporting surface, and when the chair is tilted whereby at least one castor is raised from the supporting surface, the abutment means of other castors contacts the supporting surface with the said imaginary plane of the abutment means lying in the plane of the supporting surface. 